JPH0493393A - Nematic liquid crystal composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which can be driven at a low voltage and has excellent response characteristics by using a plurality of specified compounds as the constituents. CONSTITUTION:The title composition contains a compound having a functional group of formula I (wherein R<1> is 1-10C straight-chain alkyl; n is 1 to 5) (e.g. a compound of formula II or III) and a compound of formula IV (wherein n is 1 to 2).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a nematic liquid crystal composition useful as an electro-optical display material and a liquid crystal display device using the same.

[Conventional technology]

A typical liquid crystal display cell is a TN-LCD (twisted nematic liquid crystal display), which is used in watches, calculators, electronic notebooks, pocket convenience stores, word processors, personal convenience stores, and the like. In recent years, with the increase in information processed by office automation equipment, the amount of information displayed on a single screen has increased, and conventional TN-LCDs have been found to be particularly difficult to display in terms of display quality such as contrast and viewing angles, especially when used in word processors, personal computers, etc. It is no longer possible to meet the demand for split drive.

Under these circumstances, Chef f.
er) etc. (SID '85 Digest, P120
(1985)) or CSID '86 D for clothing etc.
igest, PL22 (1986)) by ST
N (Super Twisted Nematic)-LCD
has been developed and is beginning to be widely used in displays for high information processing such as word processors and personal convenience computers.

[Problem to be solved by the invention]

In a 5TN-LCD, control of the angle between the alignment plane and the liquid crystal molecules, that is, the pretilt angle, is an important factor that greatly affects display performance, yield, etc. when manufacturing a liquid crystal display cell.

For orientation, a method is known in which the pretilt angle is controlled to a high tilt angle of about 20' by oblique vapor deposition of SiOx, but more practically, for example, "Sunever 150" manufactured by Nissan Chemical Co., Ltd. A method is known in which the pretilt angle is controlled to about 5° by rubbing an organic film such as the above. In addition, various organic films have been developed and are used by controlling the pretilt angle to 5 to 10° by a rubbing method.

It is known that the higher the pretilt angle, the less likely stripe domains will occur and the better the yield rate during the production of liquid crystal display cells. The current situation is that it is extremely difficult to create a consistently stable alignment film.

The problem to be solved by the present invention is to provide an S
An object of the present invention is to provide a TN liquid crystal composition. That is, the object of the present invention is to provide a liquid crystal composition in which the liquid crystal itself is stably aligned at a high pretilt angle and can be driven at a low voltage, based on physicochemical considerations of liquid crystal molecules at the alignment film interface. In addition, from a quality standpoint, by encapsulating a liquid crystal display cell with a pretilt angle of approximately 5°, which can be formed with a practically stable alignment film using a rubbing method, a nematic material that can form a pretilt angle higher than 5° is used. An object of the present invention is to provide a liquid crystal composition.

[Means to solve the problem]

In order to solve the above problems, the present invention has a general formula (I) -0-(CH2), -OR', in which R1 is a linear alkyl group having 1 to 10 carbon atoms, at the end of the molecule. where n represents an integer of 1 to 5. ) (hereinafter referred to as compound (A)) and (2) - formula % formula % (in the formula, n represents 1 or 2) (hereinafter referred to as compound (A)) There is provided a nematic liquid crystal composition containing B).

The nematic liquid crystal composition composed of compounds (A) and (B) used in the present invention has a nematic phase over a wide temperature range including room temperature, and is chemically and electrically stable.

In particular, the combination of compounds (A) and (B) provides an STN liquid crystal composition that has excellent responsiveness and can be driven at low voltage.

Table 1 lists the phase transition temperatures of typical compounds (A) used in the present invention.

The content of the compound (A) used in the present invention in the nematic liquid crystal composition of the present invention is preferably in the range of 3 to 40% by weight.

Table 2 lists the phase transition temperatures of typical compounds represented by the general formula (B) used in the present invention.

Table 2 Preferred representative examples of liquid crystal compounds that can be used in combination with compound (A) and the compound represented by formula (B) used in the present invention are listed below.

The compound represented by the general formula (B) used in the present invention,
The content in the nematic liquid crystal composition of the present invention is 5 to 40
A weight percent range is preferred.

(In the above formula, R3 represents an alkyl group, R'' represents an alkyl group or an alkoxyl group, X represents a hydrogen atom or a fluorine atom, and Y represents a fluorine atom, a cyano group, an alkyl group, or an alkoxyl group. ) The nematic liquid crystal composition used in the present invention is characterized by a higher pretilt angle than when conventional liquid crystal compositions are sealed, and is a liquid crystal display cell capable of forming a pretilt angle of approximately 5°. It is not limited to.

A difference in pretilt angle of 1° makes it difficult for stripe domains to occur significantly, improving the yield rate when manufacturing STN liquid crystal display cells.

5TN-LC sealed with the nematic liquid crystal composition of the present invention
When Sample D was produced, it was confirmed that stripe domains were significantly less likely to occur, and the yield was improved.

Further, the vertically aligned liquid crystal composition of the present invention is extremely useful for all-direct alignment required in, for example, an ECB (birefringence control) type display device.

〔Example〕

The present invention will be explained in detail below with reference to Examples, but the present invention is not limited to these Examples.

In addition, in the examples, "%" represents "weight %".

Example 1 A mixed liquid crystal consisting of 15%, 15%, 10%, 10%, and 20% was prepared. The nematic phase-isotropic liquid phase transition temperature (TN-1), refractive index anisotropy (Δn), and dielectric constant anisotropy (Δε) of this mixed liquid crystal were as follows.

T: 64.9°C Δn: 0.110 Δε: 9.9 This mixed liquid crystal was combined with an alignment film formed by rubbing an organic film of “Sunever 150” manufactured by Nissan Chemical Co., Ltd. in a vertically antiparallel manner. The pretilt angle was measured by enclosing it in a cell and using a magnetic field potential method, and found that it was 7.1°.

A mixed liquid crystal consisting of 10%, 10%, 20% and 20% was prepared. The nematic phase-isotropic liquid phase transition temperature (TN-1), refractive index anisotropy (Δn), and dielectric constant anisotropy (Δε) of this mixed liquid crystal were as follows.

TN-+: 63.1°C Δn: O, LO8 Δε: 9.8 Using this mixed liquid crystal, the pretilt angle was measured in the same manner as in Example 1, and the result was 7.0''.

A mixed liquid crystal consisting of 10%, 10%, 20% and 20% Example 3 15%, 15%, 10% was prepared. The nematic phase-isotropic liquid phase transition temperature (TN-1), refractive index anisotropy (Δn), and dielectric constant anisotropy (Δε) of this mixed liquid crystal were as follows.

Tx-+: 62.7°C Δn: 0.107 Δε: 9.5 Using this mixed liquid crystal, the pretilt angle was measured in the same manner as in Example 1, and the result was 7.7°.

Comparative Example 1 A mixed liquid crystal was prepared consisting of 15%, 6%, 20%, 15%, and 20%, 6%, 6%, and 6%. The nematic phase-isotropic liquid phase transition temperature (TH-t), refractive index anisotropy (Δn), and dielectric constant anisotropy (Δε) of this mixed liquid crystal were as follows.

TN-1: 83.1°C Δn: 0.111 Δε: 6. The pretilt angle was measured in the same manner as in Example 1 using a mixed liquid crystal of 4.9°.

In all of Examples 1 to 3, the pretilt angle was increased by 1° or more compared to Comparative Example 1.

Comparative example 2 50% Added so that

Here, Δd/p is the thickness of the wedge-shaped cell at the boundary where no stripe domain occurs, dl and d2 (dl〉d,
) and 50% of the mixture was prepared, and the mixture was solid at room temperature.

Next, a mixed liquid crystal obtained by adding a chiral substance (rS-811J manufactured by Merck & Co., Ltd.) to each of the mixed liquid crystals used in Examples 1 to 3 and Comparative Example 1 was applied to the organic film of Sunever 150J on the opposing flat transparent electrode. A wedge-shaped cell with a twist angle of 220° and a display cell each having an alignment film formed by rubbing the sample were injected into a display cell, and their characteristics were measured.

Note that the chiral substance has the characteristic helical pitch P of the mixed liquid crystal and the cell thickness d of the display cell due to the addition of the chiral substance.
It is defined as Δn −d =0.85, d/p=0.53, and the larger the value, the better.

In addition, the transmittance of light perpendicular to the display cell surface is 10% and 8%.
When the voltage at which the voltage is 0% is vth and V sat, the steepness γ of the electro-optical characteristic is V sat / V t
It is defined as h, and the closer this value is to 1, the better the high time division characteristics are.

Table 3 shows the measurement results of the display characteristics of super twisted nematic liquid crystals obtained by adding chiral substances to the mixed liquid crystals prepared in Examples 1 to 3 and Comparative Example 1. In any of the mixed liquid crystals of Examples 1 to 3, stripe domains are less likely to occur than in the mixed liquid crystal of Comparative Example 1. In addition, the steepness γ is close to 1, and excellent high time division characteristics are obtained. It showed excellent liquid crystal display characteristics.

〔Effect of the invention〕

The nematic liquid crystal composition containing the compound (A) having a functional group represented by the general formula (I) at the end of the molecule and the compound represented by the formula (B) according to the present invention is a conventional nematic liquid crystal composition. Approximately 5° when mixed with other substances
The pretilt angle can be increased by encapsulating the liquid crystal display cell in a liquid crystal display cell having an alignment film capable of forming a pretilt angle of .

Therefore, the nematic liquid crystal composition according to the present invention has a significantly low incidence of stripe domains and is extremely useful as a material for 5TN-LCD, which has a good yield during LCD manufacturing.

Agent: Patent Attorney Katsutoshi Takahashi

Claims (1)

[Claims] 1. (1) At the end of the molecule, the general formula -O-(CH_2)_m-OR^1 (in the formula, R^1 represents a linear alkyl group having 1 to 10 carbon atoms; , n represents an integer from 1 to 5) and (2) general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (where n represents 1 or 2). A nematic liquid crystal composition comprising the compound represented by the formula 1. 2. A super twisted nematic liquid crystal display device using the nematic liquid crystal composition according to claim 1. 3. A liquid crystal display device, characterized in that the nematic liquid crystal composition according to claim 1 is vertically aligned.